1. AMU PAST PAPERSPHYSICS- UNSOLVED PAPER - 2002

2. SECTION I Single Correct Answer Type There are five parts in this question. Four choices are given for each part and one of them is correct. Indicate you choice of the correct answer for each part in your answer-book by writing the letter (a), (b), (c) or (d) whichever is appropriate

3. 01 Problem Suitable impurities are added to a semiconductor depending on its use. This is due to : a. Increase its electrical resistivity b. Increase its electrical conductivity c. Increase its life d. Enable it to tolerate higher voltage

4. 02 Problem When are electron and a position at rest are annihilated, then the number of photons produced is : a. One b. Two c. Four d. Any arbitray number

5. 03 Problem A convex lens of focal length 20 cm produces a real image twice the size of the object. Then the distance of the object from the lens is : a. 10 cm b. 20 cm c. 30 cm d. 40 cm

6. 04 Problem The separation between the plates of a parallel plate capacitor is d and area of each plate is A, when a slab of material of dielectric constant K and thickness t is introduced between the plates, the capacitance becomes : 0 A 1 a. d t 1 K 0 A 1 b. d t 1 K 0 A 1 d t 1 c. K 0 A 1 d t 1 d. K

7. 05 Problem When a potential difference V is applied across a conductor at temperature T, the thermal speed of electrons is proportional to : a. T b. T c. V d. O

8. 06 Problem If the electron in hydrogen atom jumps from third orbit to second orbit, the wavelength of the emitted radiation is given by a. 36 5R 56 b. 3R 5 c. R R d. 6

9. 07 Problem In Youngs double slit experiment, the fringe width is found to be 0.4 mm. If the whole apparatus is dipped in water of refractive index 4/3, without disturbing the arrangement, the new fringe width will be : a. 0.30 mm b. 0.40 mm c. 0.53 mm d. 0.2 m

10. 08 Problem The final image formed by a microscope is : a. Virtual and magnified b. Real and magnified c. Real and diminished d. Virtual and diminished

11. 09 Problem A 10 thick wire is stretched so that its length becomes 3 times. Then the new resistance of the wire is : a. 10 b. 30 c. 90 10 d. 9

12. 10 Problem Five resistance have been connected in the manner shown in figure. The equivalent resistance between points X and Y will be equal to : a. 10 b. 20 c. 60 20 d. 3

13. 11 Problem Eddy currents may be reduced by using : a. Laminated cores of steel b. Laminated core of soft iron c. Thick piece of cobalt d. Thick piece of nickel

14. 12 Problem The magnetic energy stored in an inductor coil varies with magnetic field a. B b. B2 1 c. B d. B0

15. 13 Problem The specific resistance of wire : a. Varies with its length b. Varies with its cross section c. Varies with its mass d. Is independent of length, cross section and mass of the wire

16. 14 Problem Retentively is maximum for : a. Steel b. Soft iron c. Copper d. Silver

17. 15 Problem The charactivity is maximum for: a. Amplitude b. Velocity c. Frequency d. wavelength

18. 16 Problem The focal length of a concave mirror is : a. Maximum for red colour b. Maximum for violet colour c. Maximum for yellow colour d. Same for all colours

19. 17 Problem A force F is applied on a body and it moves with a velocity , the power will be : a. F. F b. c. F. 2 F d. 2

20. 18 Problem For the same kinetic energy, the momentum is maximum for : a. An electron b. A proton c. A deutron d. An particle

21. 19 Problem Four spheres each of diameter 2a and mass M are placed with their centers on the four corners of a square of side b. The moment of inertia of the system about any side of the square will be : 8 a. 5 Ma2 + 2Mb2 8 b. 5 Ma2 + Mb2 8 c. 5 Ma2 + 4Mb2 d. 8 Ma2 + 16Mb2 5

22. 20 Problem A ring of radius r and mass m rotates about an axis passing through its centre and perpendicular to its plane, its kinetic energy is : a. mr b. 1 mr 2 2 c. mr2 2 1 d. 2 mr2 2

23. 21 Problem If the speed of the rotation of earth increases, then the weight of the body. a. Increases b. Decreases c. Remains unchanged d. May increases or decrease

24. 22 Problem An organ pipe P1 closed at one end and vibrating in its first overtone and another pipe P2 open at both ends vibrating in its second overtone are in resonances. The ratio of length of pipes P1 and P2 is : a. 1 b. 1/2 c. 1/3 d. 3/4

25. 23 Problem The equation of a wave traveling in a string is given as y = 3 cos (100t -x). Its wavelength is : a. 3 cm b. 100 cm c. 2 cm d. 5 cm

26. 24 Problem A star is moving away from the earth with a velocity of 105 m/s. The shift in the spectral line of wavelength 5700 as observed on the earth is : a. 0.75 b. 1.75 c. 1.9 d. 2.01

27. 25 Problem Two sound wave are y a sin t kx y a cos(t kx) , the phase difference between the two waves is : a. /2 b. /4 c. d. 0

28. 26 Problem The velocity of sound in air is not affected by changes in : a. Moisture contents in air b. Temperature of air c. The atmospheric pressure d. The composition of air

29. 27 Problem The velocity of light in a medium of refractive index 3/2 is : a. 2 x 108 m/s b. 4 x 108 m/s c. 5 x 105 m/s d. 9 x 105 m/s

30. 28 Problem The image formed by a convex mirror is : a. Virtual, erect and diminished b. Virtual, erect and enlarged c. Real, inverted and diminished d. Real, inverted and enlarged

31. 29 Problem In a reflecting astronomical telescope, parabolic mirrors are used because they are free from : a. Spherical aberration b. Chromatic aberration c. Spherical and chromatic aberration both d. No aberration

32. 30 Problem To remove the chromatic aberration, combination of lens should be such that : a. FR + FV = 0 b. RR + FV c. FR < FV d. FR FV = 0

33. 31 Problem For a long cylindrical source of light, the illuminance E on a screen varies with distance r as : a. E r-2 b. E r-1 c. E r0 d. E r2

34. 32 Problem The radius of curvature of curved surface of a plano-convex lens is 15 cm and refractive index of lens material is 1.6. The power of the lens will be : a. 1.66 D b. 4 D c. - 1.0 D d. - 3.75 D

35. 33 Problem A beam of monochromatic blut light of wavelength 4200 in air travels in water (refractive index 4/3) its wavelength in water will be : a. 2800 b. 3150 c. 4000 d. 5600

36. 34 Problem Rays of light fall on a glass plate of refractive index . If the angle between reflected and refracted rays is 900, then the angel of incidence is : a. sin-1( ) b. cos-1( ) c. tan-1( ) d. tan-1(1/ )

37. 35 Problem A plane glass slab is placed over letters of different colours which letters appears to be raised most : a. Red b. Violet c. Yellow d. All coloured letters appear equally raised

38. 36 Problem When an ideal gas is heated at constant pressure, the fraction of the heat energy supplied, which increases the internal energy of the gas, is : 2 a. 5 3 b. 5 3 c. 7 5 d. 7

39. 37 Problem The second law of thermodynamics is concerned with the : a. Conservation of energy b. Conservation of number of holes c. Transformation of heat energy into work d. Conservation of temperature

40. 38 Problem At which of the following temperature would the molecules of a gas have twice, the average kinetic energy they have at 200C ? a. 3130C b. 3730C c. 3930C d. 5860C

41. 39 Problem An iron piece falls from a height of 1 km on the ground. If all the energy is converted into heat, the temperature of the iron piece will be (specific heat of iron = 0.1kcal/kg 0C) : a. 0.2330C b. 2.330C c. 32.80C d. 2330C

42. 40 Problem If a given mass of gas occupies a volume 100m3 at one atmospheric pressure and temperature of 1000C, What will be its volume at 4 atmospheric pressure the temperature being the same : a. 25 cm3 b. 0 c. 50 cm3 d. 5 cm3

43. 41 Problem Work done by a system is zero in : a. Isothermal process b. Adiabatic process c. Isochoric process d. Isobaric process

44. 42 Problem 1 mole of a monoatomic gas is first heated at constant volume at 1000C. The change in internal energy of the gas is u1. Next it is heated at constant pressure at 1000C, the change in internal energy of the gas is U2. Then the u1 ratio : u2 a. 1 3 b. 5 5 c. 3 d. uncertain

45. 43 Problem If the degrees of freedom of a gas are f then the ratio of its specific heats C p is C given by : 2 a. 1+ f b. 1 - 2 f c. 1 + 1 f 1 d. 1- f

46. 44 Problem In bringing an electron towards another electron, electrostatic potential energy of system : a. Decreases b. Increases c. Remains unchanged d. Becomes zero

47. 45 Problem Viscosity is most closely related to : a. Friction b. Adhesive molecular force c. Cohesive molecular force d. Bernoullis theorem

48. 46 Problem The substances which are repelled by a magnet are called : a. Diamagnetic substances b. Paramagnetic substances c. Ferromagnetic substance d. Super magnetic substance

49. 47 Problem The time constant of L-R circuit is : a. LR L b. R R c. L 1 d. LR

50. 48 Problem In a full wave rectifier, the rms value of AC component of the waves : a. Equal to DC value b. More than DC value c. Less than DC value d. Zero

51. 49 Problem The minimum wavelength of X-rays produced by electrons accelerated by a potential difference of V volts is : a. eV vc eV b. hc hc c. eV h d. v

52. 50 Problem According to Bohrs theory the relation between principal quantum number n and radius (r) of orbit : a. 1 r n b. r n c. r n2 1 d. r n2

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